Northeast Corner Research Articles

Distribution of uranium, plutonium, and 241Am in soil samples from Idaho National Laboratory

Soil materials used were collected in the early 1970s at Idaho National Laboratory near the Subsurface Disposal Area (SDA). Samples from a depth of 0–4 and 4–8 cm at two different sites located on the northeast corner of the SDA perimeter were analyzed. The concentration of 234U, 235U, 236U, and 238U in soil digests were measured by mass spectrometry. Uranium isotopic composition of the soil at the two sample sites and depths is compared to previously measured concentrations of 238Pu, 239Pu, 240Pu, 241Pu, and 241Am. Implications for remediation of contaminated soils surrounding the SDA are discussed.

Forty-year changes in the canopy and the understorey in Wytham Woods

Summary This study investigates changes in the composition of part of Wytham Woods (southern England), between the 1960s and 2007. The study focussed on an area of ~ 4 ha shown on a 1961 aerial photograph, part former open common, part ancient woodland. Changes in the canopy appearance were considered using a recent (1999) aerial photograph. Trees and shrubs were recorded in a 200 × 10 m transect to illustrate current stand structure across the historic management division. In the north-east corner of the area, tree diameters and understorey abundance from 1968 were compared with the current stand structure. Since the 1950s, Fraxinus excelsior has colonized the open areas. Tree growth was estimated from comparison of diameter/girth measurements from 1968 and 2007. F. excelsior diameter increment was greater than that of Acer pseudoplatanus and both showed faster growth than Quercus robur . Some canopy trees died, but no large gaps formed in the closed woodland. The abundance of understorey stems declined. The current stand structure refl ects effects of past management, browsing pressure and climatic stresses over the last four decades. Multiple causes of change are probably commoner than single factors in explaining woodland structure.

GEOMORPHOLOGICAL UNITS AND LANDCOVER MAP OF WADI EL-NATRUN AREA USING REMOTE SENSING AND GIS TECHNIQUES, WESTERN DESERT, EGYPT

Wadi EL-Natrun area is one of the promising areas in theWestern Desert for reclamation and utilization due to its location andthe presence of ground water in a suitable quality for irrigation. It islocated in the northeast corner of the Western Desert betweenlongitudes 30

Regional Difference‐in‐Differences in France Using the German Annexation of Alsace‐Moselle in 1870–1918

The evaluation of labor market policies has been an expanding field in the last decades. This is partly due to the increasing availability of survey data and computing power and partly to the recognition that even complex phenomena such as the impact of laws and regulations on labor markets can be rigorously tested thanks to new empiricalmethodologies, such as the so‐called difference‐in‐difference approaches (also called double differences). In this approach, the outcome (education, access to employment, unemployment rate) of a treated group, that is, a group subject to a policy change, is compared to that of a control group, that is, a group made up of individuals (or any other unit of observation) as close as possible to the treated group but unaffected by the treatment. The strategy of the researchers consists in finding a sudden change in policy and building a relevant comparison group. A recent paper by Imbens and Wooldridge (2008) discusses the issues associated with the choice of the groups and surveys the literature. In countries with a federal structure such as the United States or Canada, it is straightforward to use this technique to evaluate policy changes. Indeed, many laws are specific to a state (for the United States) or a province (for Canada). When states experiencing a reform are compared to states with no change, it is straightforward to obtain inferences about the causal effects of the reform. In contrast, researchers studying French labor laws typically face cases in which there is no geographical variance in policy changes since the main law is supposed to apply equally to all the French territory. Therefore, policy evaluation has to rely on other control groups. A consequence of this “universal”character of the law is that the evaluation of the reduction in working time in France—from

Effects of Turkish forest management philosophy and applications on forest ecosystem structure and functions in northeast Turkey: a case study in Saçinka Forest Management Planning Unit.

Nowadays, Turkish forest management philosophy has changed from timber management to ecosystem-based multiple-use forest planning (EBMUFM) with the principles of “sustainable forest management” criteria and indicators drafted in a few national and international agreements. This study analyzed the temporal changes in forest ecosystem structure and a few forest values such as tree species, distribution of age class, development stage, canopy closure, species mixture, timber volume and increment, carbon storage and oxygen production in Sacinka Forest Planning Unit in the northeast corner of Turkey. To assess the patterns during a 21-year period (1985-2006), the necessary data were obtained from forest stand maps and evaluated with Geographical Information Systems (GIS). Results showed that the decrease of agricultural and settlement areas caused the increase of productive forests and the decrease of degraded forests. Bark beetles, which have common effect in Artvin, had less effect on the vitality of Sacinka Forest Planning Unit forests compared to the neighboring forest ecosystems. This forest ecosystem vitality and integrity level was a result of the mechanic and biological interventions against the beetle damages and appropriate silvicultural prescriptions. Key words: Ecosystem based multiple use forest management planning, geographic information systems, land cover change, carbon storage, oxygen production.

Distance from the forest edge matters in habitat selection of the Blue-footed Booby Sula nebouxii

The relationships between breeding site location in forest habitat and age, behaviour and reproductive performance of Blue-footed Boobies Sula nebouxii were examined in two different plots on the northeast corner of Isla Isabel, Mexico. Birds nesting closer to the forest edge, where nest density is highest, laid their clutches earlier and fledged more chicks. In plot A, proximity to the forest edge was associated with more wakefulness and wing drooping in chicks and more interactions with other species in female breeders. In plot B, ages of breeders increased closer to the forest edge. The patterns of nest density, laying date and age distribution suggest that, on the northeast corner of Isla Isabel, the boobies prefer to nest close to the forest edge, possibly because the benefits, including easy landing and take-off, are greater than the costs associated with inclement weather, high density of conspecifics and allospecifics, and negative social interactions.

The Southern against the South: The Chicago Conspiracy in the 1932 Negro Southern Baseball League

The Negro league before and after 1932 was the Negro National League, depression and declining revenues forced the circuit to close operations that year. In its absence rose the Negro Southern League (NSL) and the East-West Colored League, and the former included the small-town Monroe Monarchs, the team's first and only year of major league baseball. The Monarchs were a minor Negro league baseball team in the early 1930s, owned by Fred Stovall, a white oil magnate. Monroe was a town of twenty-six thousand in the northeast corner of Louisiana, the hub of a poor cotton-farming region in the Mississippi Delta approximately seventy miles from the river and forty from the Arkansas border.1 Though the Monarchs won more and lost fewer games than the Chicago American Giants in that 1932 season, the League pennant was denied them. Chicago's victory has subsequently been mentioned in each of the brief statistical notations of the 1932 Negro Southern League without comment. The confusion of the season and the collapse of the National League have created unexamined assumptions about the outcomes of the year's black baseball. Twenty-first century Monroe, for example, still stands by the team's victory. No eyewitness testimony or reflective confession exists to prove that Monroe's pennant was stolen by its own league, existing evidence casts doubt on the legitimacy of the standings printed in every baseball reference book that includes the 1932 Negro Leagues. Fred Stovall wanted his Monarchs to be part of a new league in 1932, rather than the 1931 Texas League, which his team won. That organization was not headquartered in Monroe, nor was it a league, and the success of Stovall's team the previous year led the owner to make an attempt for one or the other. A white Dallas native, Stovall came to Monroe in 1917, and by 1932 owned both the Stovall Drilling Company and the J.M. Supply Company, among other enterprises, allowing him to found his black baseball team with drilling employees in 1930. He never incorporated the team, even after its success led him to hire veteran professionals. By 1932, his Monroe Black Drillers acted as a company team while the Monarchs tended largely to baseball. His first move of the 19311932 intercession was to hire business manager H.D. Doug English from the Shreveport Sports, a fellow Texas League team the previous season, to administer both the team and a possible league. He then called a meeting of potential owners in Monroe, with representatives from New Orleans, Baton Rouge, Shreveport, and Alexandria from Louisiana, Little Rock, Hot Springs, Pine Bluff, and El Dorado from Arkansas, and Vicksburg, Natchez, and Jackson from Mississippi. The Tri-State League, as the potential aggregation would be called, met on January 22. There seem[s] to be a change coming up the road, wrote Pitman E. Nedde, sports editor and columnist for the Shreoeport Sun, but don't get glad too quick - it's a little too early.2 From that first meeting came the possibility of recruiting the much more prominent Memphis Red Sox for the new league. The Kansas City Monarchs, Cuban Giants, Pittsburgh Crawfords, Indianapolis Black Caps, and Chicago American Giants - all large market franchises - were considered potential associate members (a sort of honorific that would ensure the teams barnstormed through the new circuit). Monroe, New Orleans, Little Rock, and Jackson, known as the Big Four, formed the nucleus of the potential league, and each team chose a representative to scout the region surrounding its city to investigate the conditions of other applicant towns. The Louisiana Weekly reported, Many prominent white men seem interested in this movement and appear willing to help put this project over. However, by mid-February, the smaller market, originally-invited teams could not meet the monetary guarantee and the franchise purchase requirement, leaving only the larger area cities to field teams. …

Fire and Ice: Unnatural Disasters and the Disposable Urban Poor in Post‐Apartheid Johannesburg

AbstractJohannesburg is a divided city where propertied middle‐class residents and the urban poor live in existentially separate worlds. If the steady accretion of luxury entertainment sites, enclosed shopping malls and gated residential communities in the northern suburbs has come to symbolize the entry of middle‐class urbanites into the culture of aspirant ‘world class’ cities, then the proliferation of overcrowded, resource‐starved informal settlements on the periurban fringe represents the dystopian features of distressed urbanism. The risk‐prone environments of informal squatter settlements magnify the impact of catastrophic events like fires and floods, and the intersection of disaster‐vulnerable settlement patterns with relaxed planning regulations and building standards, lack of preparation for unsuspected calamities, and inadequate crisis management creates entirely new artificial hazards. These unnatural disasters cannot simply be attributed to ‘bad luck’ or nature's destructive force. Disaster‐vulnerability and exposure to risk are unevenly distributed across the metropolis. By focusing attention on the catastrophic fires that regularly destroy shanty settlements in places like Alexandra township at the northeast corner of Johannesburg, it is possible to reveal a largely hidden structure of marginality and social insecurity that is a permanent condition of everyday life for the urban poor.Résumé Johannesburg est une ville divisée où habitants de la classe moyenne possédante et citadins pauvres vivent dans des univers d’existence séparés. Si l’augmentation régulière des lieux de distractions, centres commerciaux et enclaves privées sécurisées dans les banlieues Nord signe l’accès des citadins de la classe moyenne à la culture des villes candidates à‘l’échelon international’, la prolifération d’implantations sauvages surpeuplées et dépourvues de ressources à la limite périurbaine traduit les caractères dystopiques d’un urbanisme sinistré. Les environnements à risque des implantations sauvages des squatters amplifient l’impact des catastrophes telles que les incendies ou inondations, tandis que la conjonction entre modèles d’implantations à risque assortis de réglementations d’urbanisme et de normes de construction assouplies, préparation insuffisante à des calamités insoupçonnées et gestion inappropriée des crises, crée des risques artificiels totalement nouveaux. On ne peut attribuer ces désastres non naturels simplement à la malchance ou à la force destructrice de la nature. La vulnérabilité face aux catastrophes et l’exposition au risque ne se répartissent pas uniformément dans la métropole. En s’intéressant aux incendies qui ravagent régulièrement les bidonvilles existants, comme le township d’Alexandra dans la zone nord‐est de Johannesburg, on peut mettre à jour une structure quasi invisible de marginalité et d’insécurité sociale qui constitue un état permanent dans la vie quotidienne des citadins pauvres.

First Report of Northern Mole Cricket Damage on a Nebraska Golf Course (Orthoptera: Gryllotalpidae)

The northern mole cricket, Neocurtilla hexadactyla (Perty) (Orthoptera: Gryllotalpidae), is native to North America and is widely distributed across the eastern two thirds of the United States from southern Canada to Florida in the east and South Dakota to Texas including the northeast corner of Colorado in the west (Capinera, 2004). Based on Nebraska State Insect Records (nebrecs.unl.edu, accessed February 1, 2008), the first report of N. hexadactyla in Nebraska was from Saunders County in 1909. It is currently known from 61 of Nebraska’s 93 counties (Fig. 1). Mole crickets (especially the tawny mole cricket, Scapteriscus vicinus Scudder, southern mole cricket, S. borellii Giglio-Tos, and short-winged mole cricket, S. abbreviatus Scudder) are important pests of turfgrasses in southeastern regions of the United States (Brandenburg and Villani, 1995; Potter, 1998; Vittum et al., 1999). During the summer of 2007, northern mole crickets were observed damaging a Penncross creeping bentgrass, Agrostis palustris Huds. (Family Poaceae), putting green on a golf course in Butler County, Nebraska. This is the first known report of northern mole crickets causing significant damage to golf course turf in Nebraska, and is noteworthy because N. hexadactyla is rarely, if ever, considered a pest of turfgrasses (Vittum et al., 1999). Little is known about the biology, ecology, and life history of N. hexadactyla in Nebraska and the midwest. Like most mole crickets, N. hexadactyla seems to prefer moist low-lying areas and is often found along the margins of lakes and streams. The 2007 infested putting green was adjacent to a water hazard, consistent with previous environmental habitat observations. Foraging adults and immatures of mole cricket species burrow in damp loose soil and feed on the roots of plants. This tunneling behavior can cause considerable disruption to highly maintained turfs such as putting greens (Vittum et al., 1999). Soil at the 2007 infested green consisted of approximately one cm sand

Florida river flow patterns and the Atlantic multidecadal oscillation

AbstractA major step in developing legislatively mandated ecological flows for watercourses in Florida, USA is the selection of an appropriate baseline flow period. Recently climatologists have established a link between multidecadal periods of warming and cooling of the Atlantic Ocean (the Atlantic Multidecadal Oscillation (AMO)) and rainfall patterns across much of North America. During an AMO warm period (pre‐1970), much of North America received less than average rainfall, while during a multidecadal cool period (post‐1970), much of North America experienced above normal rainfall. There are exceptions to this general trend with some areas of North America showing an opposite relationship with the AMO. Peninsular Florida is one of these exceptions. While analysing flows on a number of rivers in south–central Florida, we observed a step rather than a monotonic trend in flows consistent with a switch from a warm multidecadal period to a cool multidecadal period. We examined river flows at all gaging sites throughout Florida and the southeast United States that had flow records of 60 years or more. Three river flow patterns were clearly discerned: a Southern River Flow Pattern (SRP) where flows are seasonally greatest during the summer months (June–September); a Northern River Flow Pattern (NRP) where flows are seasonally greatest in the spring and a Bimodal River Flow Pattern (BRP) with distinct peaks in rainfall and flow both in spring and summer. Those rivers with a BRP occur in a band that stretches diagonally from the northeast corner of Florida (St. Marys River) and runs in a southwest direction to the big bend area of the state near the mouth of the Suwannee River. Rivers to the north of this line exhibit the NRP, while rivers to the south of this line exhibit the SRP. Rivers with the SRP exhibited consistently lower flows during the AMO cool period and consistently higher flows during the AMO warm period. Differences in flow volumes between multidecadal periods averaged 30% in SRP rivers. Rivers with a NRP showed an opposite trend. Most convincingly, rivers with the BRP exhibited both trends, the spring mode responded similarly to the northern rivers while the summer mode followed the southern river trend. These results have important implications not only for the establishment of ecological flows, but also for water supply planning and development, flood control and stream ecology in general, since there are considerable differences in the magnitude of flows that should naturally be expected between multidecadal periods. Relatively large decreases and increases in flow are attributable to rainfall differences between multidecadal periods. Copyright © 2008 John Wiley & Sons, Ltd.

Hydrography, currents and distribution of suspended matter during a dumping experiment in the western Baltic Sea at a site near Warnemünde

During a dumping experiment on 20/21 June 2001, an extensive data record was collected to understand the dynamical processes in the water column of the investigation area and to validate model results. Weak westerly winds with strongly changing cloud coverage characterized the meteorological situation. During the second day the wind calmed down and moved shortly to easterly directions. The water column was characterized by a strong vertical stratification with discontinuity layers in temperature and salinity in 12 and 16 m. The current regime was dominated by outflow at the water surface and inflow along the German coast, with strong current shearing in the dumping area. The suspended matter clouds could be identified by optical methods and ADCP (Acoustic Doppler Current Profiler) scattering intensity. During the experiment the suspended matter plumes were only visible at the surface up to 1 h after the dumping. The aerial photographs document that the particle clouds at the surface drifted to the west and, after approximately 40 min, they were only weakly visible. The fine material was concentrated in the discontinuity layer leading to substantially higher values of optical parameters and suspended matter concentration than measured in the surface clouds. Due to the vertical current shears the material was transported in the water column in different directions. At the first day the maximum of the suspended matter in the discontinuity layer was in the north-western corner and in the bottom layer in the northeast corner of the dumping area. Strong wind conditions after the dumping led to periodical resuspension processes.

Using neutron activation analysis to identify scales of interaction at Kinet Höyük, Turkey

We use NAA to characterize a relatively large archaeological ceramic sample from the Late Bronze Age to Hellenistic phases of Kinet Höyük, a coastal Turkish site in the Gulf of Iskenderun at the northeast corner of the Mediterranean Sea. The geographic extent of local Kinet wares (how local is local?) is established through comparison with sediment samples across the Kinet hinterland. Four major compositional groups are identified: local and locally imported wares, imports from Cypriot, and presumed Western Anatolian and Aegean centers, and imports that appear relatively homogenous elementally but comprise typologically diverse ceramics with attributions that range from Cyprus to the coastal mainland. Comparison with other published NAA studies for this site reinforces the elemental evidence for local production, and underlines the need for caution when assuming local production always equates with local clays particularly for coastal sites. We propose that the chronological distribution of the local and non-local groups provides a useful political economic proxy. The study indicates systemic and widespread political disruption and marginalization at the transition to the Late Iron Age in this region.

War Memorials Encourage Reflection, Pride

War Memorials Encourage Reflection, Pride

Sea scallop mass mortality in a Marine Protected Area

A mass mortality of the sea scallop Placopecten magellanicus occurred between 2004 and 2005 in the Nantucket Lightship Closed Area (NLCA), a Marine Protected Area (MPA) in the Great South Channel, USA. On a broad scale (3951 km 2 ), scallop density (ind. m -2 ) in the MPA declined by 35%. On a fine scale (504 km 2 ), in the northeast corner of the MPA where most scallops occur, density declined by 50%. The scallops that perished were large and probably old; 80% had shell heights >130 mm (H ∞ = 155 mm). Only 6% of the decline in the northeast corner was explained by fishing mortality. The mass mortality equaled approximately 6484 metric tons of harvestable scal- lop meat (equivalent to US $100 million ex-vessel). Closing the NLCA to fishing in 1994 removed fish- ing mortality, increasing scallop survival rates. Scallops that recruited in 1994 reached 10 yr of age in 2004. Individuals of this age may suffer the effects of senescence, including parasitism by shell bor- ers and prokaryotic infection, which likely caused the mass mortality. If MPAs are used to manage fisheries, surveys with the accuracy and precision to resolve population dynamics on the spatial scale of the MPA are required or the benefits may be offset by increases in natural mortality.

Isotopic Studies of Contaminant Transport at the Hanford Site, Washington

Processes of fluid flow and chemical transport through the vadose zone can be characterized through the isotopic systematics of natural soils, minerals, pore fluids, and groundwater. In this contribution, we first review our research using measured isotopic variations, due both to natural and site‐related processes, of the elements H, O, N, Sr, and U, to study the interconnection between vadose zone and groundwater contamination at the Hanford Site in south‐central Washington State. We follow this brief review with a presentation of new data pertaining to vadose zone and groundwater contamination in the Waste Management Area (WMA) T‐TX‐TY vicinity. Uranium isotopic data for the C3832 core (WMA TX) indicate the involvement of processed natural U fuel and link the observed U contamination to releases near single‐shelled tank TX‐104. The data also preclude contamination from an early 1970s TX‐107 leak. In the case of the C4104 core (WMA T), the U isotopic data indicate a mixture of processed natural and enriched U fuels consistent with the major leak from T‐106 in 1973. Uranium and strontium isotopic data for the cores also provide direct evidence for chemical interaction between high‐pH waste fluid and sediment. Isotopic data (δ15N and δ18O) for groundwater nitrate contamination in multidepth samples just to the northeast of WMA T are distinct from that seen in surrounding wells and suggest tank waste (possibly from the 1973 T‐106 event) as a source of very high 99Tc concentrations recently observed at the northeast corner of WMA T.

Channel Tunnel Rail Link section 2: King's Cross lands

Section 2 of the Channel Tunnel Rail Link – now known as High Speed 1 – emerges from tunnels at the north-east corner of King's Cross lands in London and then sweeps across into St Pancras station at the south west. This paper reports on the major rail network that has been constructed in ‘area 100’ to enable train services to approach the extended St Pancras station, and also interconnect with other railway networks, thus facilitating high-speed rail services north of London. It describes the engineering objectives and the civil and railway construction works needed to achieve this complex railway network.

Declining groundwater level and aquifer dewatering in Dhaka metropolitan area, Bangladesh: causes and quantification

Large abstraction by water-wells has been causing a linear to exponential drop in groundwater level and substantial aquifer dewatering in Dhaka, Bangladesh. The city is almost entirely dependent on groundwater, which occurs beneath the area in an unconsolidated Plio-Pleistocene sandy aquifer. Analysis shows that the pattern of water-level change largely replicates the patterns of change in the rate of groundwater abstraction. Contribution of the aquifer storage to the abstraction is estimated to be more than 15% in the year 2002. This abstraction has caused a sharp drop in water level throughout the city and turned into two cones of depression in the water level. Upper parts of the aquifer are already dewatered throughout the area, with the exception of part of the northeast and southeast corner of the city. It is calculated that about 41 million cubic metres (MCM) of the aquifer dewatered by the year 1988, which increased to 2,272 MCM in the year 2002. Water-level decline may increase non-linearly due to limiting vertical recharge in areas where the aquifer is dewatered and may severely threaten the sustainability of the aquifer.

How many populations set foot through the Patagonian door? Genetic composition of the current population of Bahía Blanca (Argentina) based on data from 19 Alu polymorphisms

The city of Bahía Blanca occupies a strategic place in Argentina south of the Pampean region in the north-east corner of the Patagonia. Since 1828, this city has been the historical and political border between Amerindian lands in the south, and the lands of European colonists. Nowadays, Bahía Blanca is an urban population mainly composed by descendents of immigrants from Spain and other European countries with apparently low admixture with Amerindians. In view of the unexpectedly high Amerindian admixture levels (about 46.7%) suggested by mtDNA data, and protein markers (19.5%), we analyzed a set of 19 Alu polymorphisms (18 autosomal, 1 of Chromosome Y) in a well-documented genealogical sample from Bahía Blanca. The genotyped sample was made up of 119 unrelated healthy individuals whose birth place and grandparent origins were fully documented. According to available genealogical records, the total sample has been subdivided into two groups: Bahía Blanca Original (64 individuals with all 4 gandparents born in Argentina) and Bahía Blanca Mix (55 individuals with one to three grandparents born out of Argentina). Allele frequencies and gene diversity values in Bahía Blanca fit well into the European ranges. Population relationships have been tested for 8 Alu markers, whose variation has been described in several Amerindian and European samples. Reynolds genetic distances underline the significant genetic similarity of Bahía Blanca to Europeans (mean distance 0.044) and their differentiation from Amerindians (0.146). Interestingly enough, when the general sample is divided, Bahía Blanca Original appears slightly closer to Amerindians (0.127) in contrast to Bahía Blanca Mix (0.161). Furthermore, the genetic relationships depicted through a principal components analysis emphasize the relative similarity of Bahía Blanca Original to Amerindians. A thorough knowledge of the sample origins has allowed us to make a subtle distinction of the genetic composition of Bahía Blanca.

The Role of Intraseasonal Variability in the Nature of Asian Monsoon Precipitation

Abstract The structure of the mean precipitation of the south Asian monsoon is spatially complex. Embedded in a broad precipitation maximum extending eastward from 70°E to the northwest tropical Pacific Ocean are strong local maxima to the west of the Western Ghats mountain range of India, in Cambodia extending into the eastern China Sea, and over the eastern tropical Indian Ocean and the Bay of Bengal (BoB), where the strongest large-scale global maximum in precipitation is located. In general, the maximum precipitation occurs over the oceans and not over the land regions. Distinct temporal variability also exists with time scales ranging from days to decades. Neither the spatial nor temporal variability of the monsoon can be explained simply as the response to the cross-equatorial pressure gradient force between the continental regions of Asia and the oceans of the Southern Hemisphere, as suggested in classical descriptions of the monsoon. Monthly (1979–2005) and daily (1997–present) rainfall estimates from the Global Precipitation Climatology Project (GPCP), 3-hourly (1998–present) rainfall estimates from the Tropical Rainfall Measuring Mission (TRMM) microwave imager (TMI) estimates of sea surface temperature (SST), reanalysis products, and satellite-determined outgoing longwave radiation (OLR) data were used as the basis of a detailed diagnostic study to explore the physical basis of the spatial and temporal nature of monsoon precipitation. Propagation characteristics of the monsoon intraseasonal oscillations (MISOs) and biweekly signals from the South China Sea, coupled with local and regional effects of orography and land–atmosphere feedbacks are found to modulate and determine the locations of the mean precipitation patterns. Long-term variability is found to be associated with remote climate forcing from phenomena such as El Niño–Southern Oscillation (ENSO), but with an impact that changes interdecadally, producing incoherent responses of regional rainfall. A proportion of the interannual modulation of monsoon rainfall is found to be the direct result of the cumulative effect of rainfall variability on intraseasonal (25–80 day) time scales over the Indian Ocean. MISOs are shown to be the main modulator of weather events and encompass most synoptic activity. Composite analysis shows that the cyclonic system associated with the northward propagation of a MISO event from the equatorial Indian Ocean tends to drive moist air toward the Burma mountain range and, in so doing, enhances rainfall considerably in the northeast corner of the bay, explaining much of the observed summer maximum oriented parallel to the mountains. Similar interplay occurs to the west of the Ghats. While orography does not seem to play a defining role in MISO evolution in any part of the basin, it directly influences the cumulative MISO-associated rainfall, thus defining the observed mean seasonal pattern. This is an important conclusion since it suggests that in order for the climate models to reproduce the observed seasonal monsoon rainfall structure, MISO activity needs to be well simulated and sharp mountain ranges well represented.

Explorations of the Annual Mean Heat Budget of the Tropical Indian Ocean. Part I: Studies with an Idealized Model

Abstract Annual mean net heat fluxes from ocean general circulation models (OGCMs) are systematically too low in the tropical Indian Ocean, compared to observations. In the models, only some of the geostrophic inflow replacing southward Ekman outflow is colder than the minimum sea surface temperature (MINSST). Observed heat fluxes imply that much more inflow is colder than MINSST. Since inflow below MINSST can only join the surface Ekman transport after diathermal warming, the OGCMs must underestimate diathermal effects. A crude analog of the annual mean Indian Ocean heat budget was generated, using a rectangular box model with a deep “Indo–Pacific” gap at 7°–10°S in its eastern side. Wind stress was zonal and proportional to the Coriolis parameter, so Ekman transport was spatially constant and equaled Sverdrup transport. For three experiments, zonally integrated Ekman transport was steady and southward at 10 Sv (Sv ≡ 106 m3 s−1). In steady state, a 10 Sv “Indonesian Throughflow” fed a northward western boundary current of 10 Sv, which turned eastward along the northern boundary at 10°N to feed the southward Ekman transport. Most diathermal mixing occurred within an intense eddy in the northwest corner. Some of the geostrophic inflow was at temperatures colder than MINSST (found at the northeast corner of the eddy); it must warm to MINSST via diathermal mixing. Northern boundary upwelling exceeded the 10-Sv Ekman transport. The excess warms as it recirculates around the eddy, apparently supplying the heat to warm inflow below MINSST. In an experiment using the “flux-corrected transport” (FCT) scheme, diathermal mixing occurred in the strongly sheared currents around the eddy. However the Richardson number never became low enough to drive strong diathermal mixing, perhaps because (like that of other published models) the present model’s vertical resolution was too coarse. In three experiments, the dominant mixing was caused by horizontal diffusion, spurious convective overturn, and numerical mixing invoked by the FCT scheme, respectively. All three mixing mechanisms are physically suspect; such model problems (if widespread) must be resolved before the mismatch between observed and modeled heat fluxes can be addressed. However, the fact that the density profile at the western boundary must be hydrostatically stable places a lower limit on the area-integrated heat fluxes. Results from the three main experiments—and from many published OGCMs—are quite close to this lower limit.